The present invention relates generally to D.C. power supplies and more specifically to a computer power supply having a safety power turnoff function.
As shown in FIG. 1, a known computer D.C. power supply comprises a main AC-DC converter 1 connected to a mains A.C. voltage source to feed D.C. power voltage to the various parts of the computer including CPU 4. AC-DC converter 1 is made up of a transformer, a rectifier connected thereto and a voltage stabilizing circuit to keep the output DC voltage at constant level. To avoid possible damage on a hard disk, the timing of shutdown of the computer is determined by the CPU 4. When the CPU makes this determination, it issues a command signal to a control 3 to allow it turn off the AC-DC converter 1. Since the control circuit 3 needs to be isolated from the AC voltage source in order to process the command signal, an auxiliary AC-DC converter 2 identical to AC-DC converter 1 is connected to the AC voltage source to supply power to the control circuit 3. However, the use of an additional AC-DC converter for powering the control circuit is not desirable from the view points of size and cost performance.